1. Field of the Invention
Embodiments of the present invention generally relate to systems for coupling bone portions across a fracture and, in some embodiments, to intramedullary nail or plate and screw assemblies or other stabilizing structures, deployable materials, and/or fastening assemblies used to treat fractures of long bones, such as the femur, humerus, tibia, and various periarticular fractures of these and other bones.
2. Related Art
There are a variety of devices used to treat fractures of the femur, humerus, tibia, and other long bones. For example, fractures of the femoral neck, head, and intertrochanteric region have been successfully treated with a variety of compression screw assemblies, which include generally a compression plate having a barrel member, a lag screw and a compressing screw. In such systems, the compression plate is secured to the exterior of the femur, and the barrel member is inserted in a predrilled hole in the direction of the femoral head. The lag screw has a threaded end, or another mechanism for engaging bone, and a smooth portion. The lag screw is inserted through the barrel member so that it extends across the break and into the femoral head. The threaded portion engages the femoral head. The compression screw connects the lag screw to the plate. By adjusting the tension of the compression screw, the compression (reduction) of the fracture can be varied. The smooth portion of the lag screw is free to slide through the barrel member to permit the adjustment of the compression screw. Some assemblies of the prior art use multiple screws to prevent rotation of the lag screw relative to the compression plate and barrel member and also to prevent rotation of the femoral head on the lag screw.
Intramedullary nails in combination with lag screws or other screw assemblies have been successfully used to treat fractures of the femur, humerus, tibia, and other long bones as well. A significant application of such devices has been the treatment of femoral fractures. A typical prior art intramedullary nail may have one or more transverse apertures through its distal end to allow distal bone screws or pins to be screwed or otherwise inserted through the femur at the distal end of the intramedullary nail. This is called “locking” and secures the distal end of the intramedullary nail to the femur. In addition, a typical intramedullary nail may have one or more apertures through its proximal end to allow a lag screw assembly to be screwed or otherwise inserted through the proximal end of the intramedullary nail and into the femur. The lag screw is positioned across the fracture in the bone and an end portion of the lag screw engages the femoral head. An intramedullary nail can also be used to treat shaft fractures of the femur or other long bones.
As with compression hip screw systems, intramedullary nail systems are sometimes designed to allow compression screws and/or lag screws to slide through the nail and thus permit contact between or among the bone fragments. Contact resulting from sliding compression facilitates faster healing in some circumstances. In some systems, two separate screws are used in order to prevent rotation of the femoral head relative to the remainder of the femur, to prevent penetration of a single screw beyond the femoral head, and to prevent a single screw from tearing through the femoral neck and head. When an additional screw or pin is used, however, unequal forces applied to the separated screws or pins may cause the separate screws or pins to be pressed against the sides of the holes through which the separate screws or pins are intended to slide. This may result in binding, which may reduce or eliminate the sliding of the screws or pins through the nail. Conversely, a problem can result from excessive compression of the femoral head toward or into the fracture site. When excessive sliding compression occurs it may cause the femoral head to collapse into the trochanteric region of the femur.
In summary, and without limitation, the foregoing shows some of the shortcomings of the state of the art in this field. Among other things, what is needed is an orthopaedic implant system that includes a superior sliding screw or other mechanism for applying compression across a fracture. Some embodiments would also provide a sliding screw or other mechanism that obtains adequate bone purchase while reducing the incidence of cut-out, rotational instability, and excessive sliding. Additionally, an improved implant system could include a sliding screw (or other type of fastener/engaging member) in combination with intramedullary nails of various designs, in combination with plates, or in combination with various types of deployable materials. Combinations of any of these with each other or combinations of each other, and/or with other devices or combinations of them also present opportunities for advancement beyond the state of the art according to certain aspects of the present invention.